The design of the joint in the assembly of separated parts has become an important research area, because the structural efficiency of the structure is established, with few exceptions, by its joints, not by its basic structure.
There are two kinds of joints : mechanical and bonded. Since the adhesive bonded joints are enable to distribute the load over a larger area than the mechanical joints, require no hole, add very little weight to the structure, and have superior fatigue resistance, in this work, the analysis was confined to the adhesive bonded joints, even though, they require careful surface treatments of the adherends, are affected by service environments, and are difficult in disassembling for inspection and repair.
There are several types of adhesive joints, such as the single lap joint, the double lap joint, the stepped lap joint, and the scarfed lap joint. Among these, the single lap joint is most popular, due to its easiness of manufacturing and its relatively low cost.
The adhesively bonded joint shows large nonlinear behavior in the load-displacement relation, because structural adhesives for the joint are usually rubber toughened, which endows adhesives with nonlinear properties. Since the majority of load transfer of the adhesively bonded joint is accomplished by the nonliear behavior of the adhesive, its load transfer capability should be calculated using nonlinear properties.
In this thesis, the static torque capacity of the adhesive bonded tubular single lap joint was investigated experimentally and theoretically with respect to the bonding thickness. In order to match the calculated torque capacity of the joint to the experimentally determined one, a failure model of the adhesive was proposed according to the magnitude of the fabrication thermal residual stresses which were functions of the adhesive bonding thickness and the size of the joint. The adhesive failure model was incorporated with the nonlinear behavior of the adhesive and the different failure modes in which the adhesive failure mode changed from bulk shear failure, via transient failure, to interfacial failure between the adhesive and the adherend as the magnitude of the thermally induced residual stresses from the fabrication increased.
Although the adhesively bonded joints under static torque can be designed using the finite element method which can incorporate the material nonlinearity of adhesive, the fatigue characteristics of adhesively bonded joints are indispensable because adhesively bonded joints are usually used in dynamic loading conditions.
With the measured fatigue life, another failure model for the adhesively bonded tubular single lap joints with steel-steel adherends was developed to predict the fatigue torque transmission capability.
In order to enhance both the accuracy and speed of the estimation of the torque transmission capability, an iterative method was developed to estimate stress distributions in the adhesive layer with nonlinear properties. Due to very short processing time, the iterative solution was found to be applicable in the design and optimization of the adhesively bonded tubular single lap joint with nonlinear shear properties as an on-line design tool.
Using the static failure model, the method for the optimal design of the torque transmission capabilities of the adhesively bonded tubular single lap joint were suggested. Also, a design method for the adhesively bonded tubular single lap joint under torsional fatigue loading was proposed.
Using the developed static and fatigue failure model for the adhesively bonded tubular single lap joint, a high speed composite main spindle of the machine tool was designed as an example to apply the models in the fields. The design parameters of the adhesively bonded joint of the high speed main spindle satisfying the specifications of that were determined.